Mouse Model of Heart Organ Care System to Study Ex Vivo Cardio Protection and Reperfusion in Cadaveric Heart Donation

Objectives: Since heart and lung OCS has been developed, it became possible to improve cold ischemia time and prolong time between organ donation and transplantation. Unfortunately, large animal protocols on organ care require the same amount of resources as required in clinic. Mouse models have proven to be cost-effective and diversity of highly sensitive and specific murine reagents, as well as availability of knock-in/out mice has made them a strong research tool in many fields. Therefore, the aim of our study was to develop and test miniaturized murine heart OCS protocol.

Methods: Circuit consisted of customized capillary peristaltic pump providing flow from 100 to 600 µL/min with priming volume below 100 µL, micro-oxygenator with priming volume of 150 µL, air-trapper with priming volume of 100 µL, custom-build heat exchanger with priming volume of 200 µL, 5 mL perfusion reservoir, capillary tubing with internal diameter of 0.6 mm, and perfusion cannulas with external diameter of 0.5 mm. C 57Bl/6 animals were used as donor. For cadaveric organ donation, animals were subjected to cervical dislocation under isoflurane anesthesia. After death was confirmed, 5 mL of cardioplegic mixture containing 4°C cold heparinized Krebs–Henseleit solution has been infused directly via thoracic aorta and second over inferior vena cava. To prevent clot formation, 500 µg of recombinant tissue plasminogen activator has been added to preservation solution. The drained blood has been collected and kept in the 4°C refrigerator for 30 minutes. In 30 minutes after death, the murine heart has been explanted, and aorta has been cannulated. Perfusion solution contained to 37°C prewarmed mixture of heparinized animal blood mixed with calcium-enriched Krebs–Henseleit solution. FiO₂ on the oxygenator was set up to 100% with the flow of 0.5 L/min.

Result: Heart function recovered immediately after reperfusion and biventricular activity has been maintained for more than 4 hours. Despite cadaveric heart donation, fibrinolytic agent allowed to prevent blood clotting in the coronary system, thus improving reperfusion protocol reproducing clinically relevant human OCS protocol.

Conclusion: Unlike the Langendorff model and similarly with patient OCS, we used oxygenator and heat exchanger and performed full recirculation of the perfusion mixture in the circuit. Despite no standard heart cardioplegia has been used, the heart recovery was substantial. We believe that implementing of our straightforward model of murine OCS can valuably contribute to organ care studies.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
19 February 2021